The invention relates in general to munitions and in particular to compliance with Insensitive Munitions (IM) standards. IM standards require that, to the extent practicable, munitions are safe when subjected to unplanned stimuli. The Fast Cook Off (FCO) test is used to simulate a situation wherein munitions are exposed to a fire. In FCO, munitions are engulfed in a flame of at least 1700° C. until the munition reacts. It is desirable for the reaction to be limited to no more than burning (Type 5 IM reaction). A detonation type of reaction (Type 1 IM reaction) is to be avoided. During a FCO test, munitions with no IM features typically demonstrate a Type 1 IM detonation in less than ten minutes.
In some cases, the IM features of a munition require a slow heating to function properly. In other cases, where a complete IM solution is not viable, an improvement such as delaying the onset of the Type 1 IM reaction is desirable.
Known munition and ammo containers have several forms, including boxes and tubes. Some of these containers have IM features for the venting of gases or for insulating the munition. The venting of gases may increase the delay time to detonation. Insulating a munition, by itself, has a minimal effect on the delay time to detonation. One known munition container is made of a composite glass-reinforced resin with meltable salts. As the salts melt, they absorb heat. However, resin or plastic containers are often not suitable for munitions because the containers do not meet leak test standards after the containers are thermally cycled. Some commercial fireproof safes and fireproof doors use a layer of felt that is impregnated with a water-based hydrogel as a means to mitigate heat damage.
IM venting is not feasible for some munitions. For example, the AT4 single-shot recoilless weapon is stored with the propellant in the weapon. The propellant in the AT4 is contained in its barrel, between the warhead and a counter mass. Without venting and when exposed to conditions like the FCO test, munitions such as the AT4 will detonate quickly. There is not enough time prior to detonation to evacuate or rescue nearby personnel. In some munitions, even if IM vents are present, the heating may occur distal from the IM vent and the munition may detonate before the IM vent has activated. The heating rate in situations like the FCO test is so rapid that there may not be enough time for the IM features to function prior to detonation.
A need exists for an apparatus and method for delaying the detonation time of munitions exposed to a FCO test.